Doesn't look particularly warm to me on the output at the moment. Yes the SE of England may see some very pleasant temperatures next week but the CET area is likely to be quite a bit cooler. Although it could be a fairly Atlantic dominated month the winds look like they will often come from the W or NW so not much of a southerly element to drag up warmer air from the tropics.
Can't really see us getting anywhere near 12C as things stand. Both 2011 and 2013 which were well above 12C had very warm starts. 2014 was a bit different and was warm at times throughout. Current output suggests the CET will only exceed 12C twice in the first two weeks.
I will go for 10.9C